Plasterers&#39; darby



May 28, 1968 R. D. MALTESE PLAS'IERERS DARBY Filed July 18, 1966 INVENTOR ROY D. MALT ESE VJWM ATTOR Y NEYS 2 United States Patent Office Patented May 28, 1968 3,384,917 PLASTERERS DARBY Roy B. Maltese, 21183 W. Outer Drive, Dear-born, Mich. 4812.4 Filed July 18, 1966, Ser. No. 565387 4 Qlaims. (Cl. -2354) ABSTRACT OF THE DISCLOSURE This plasterers darby consists of an elongated body which is very thin in proportion to its width and length and which, by being made in whole or in part of fibrous material, such as fibrous glass impregnated with synthetic resin, is much lighter, thicker and wider and more easily manipulated than conventional aluminum or magnesium darbies; also, because of its resilience, it returns to its original shape if dropped, without undergoing a permanent deformation as in the case of metal darbies; also, because of its chemical inertness, it does not react with plaster as do metallic darbies and consequently possesses a minimum of plaster adhesion and is therefore more easily cleaned; and furthermore, by reason of its wedge shape or offset shape, is easy to grasp in the fingers and manipulate.

The wedge-shaped darby of FIGURES 1 and 2 herein is now described and claimed in my divisional application hereof Ser. No. 669,778, filed Sept. 22, 1967, for Plasterers Darby.

In the drawings:

FIGURE 1 is a top plan view of a wedge-shaped darby according to one form of the invention, with the central portion omitted to conserve space;

FIGURE 2 is a left-hand end elevation of the darby shown in FIGURE 1;

FIGURE 3 is a top plan view of a modified offset double-bladed darby according to the invention, with the central portion also omitted to conserve space; and

FIGURE 4 is a left-hand end elevation of the offset double-bladed darby of FIGURE 3.

Referring to the drawing in detail, FIGURE 1 shows a wedge-shaped lasterers darby, generally designated 10, of any suitable length, for example four feet, and composed of an outer layer 12 of plastic-impregnated fibrous material, such as fibrous glass, preferably in woven fabric form and surrounding a core 14 of substantially rigid foam plastic material, such as polystyrene, urethane, epoxy or phenolic synthetic resin in foam. Balsa wood may also be used for the core 14. The outer layer 12 is conveniently made up of a plurality of layers of fibrous material impregnated with synthetic resin such as polyester or epoxy resin. Rayon or nylon fibers, as well as metal strand or wire may also be used to replace glass fibers in the outer layer 12. The darby 10 of FIGURES 1 and 2 is of wedgeshaped cross-section with a thick rearward edge 16 and a thin straight forward edge 18 interconnected by upper and lower faces 20 and 22 eXtending between opposite ends 24. In actual practice, thicknesses of 0.75 inch and 0.15 inch for the thick edge 16 and thin edge 18 respectively, with a width of 5.75 inches and a length of 48 inches, has been found suitable. These dimensions are given by way of example rather than limitation.

In the use of the wedge-shaped darby 10, the operator grasps it with the portion adjacent the thick edge 16 between his fingers and draws it over the surface of the plaster after the plaster has been applied with a plasterers trowel from a plasterers hawk. The outer layer 12 is found to wear better than darbies of conventional materials, and the darby 10 with the foam core 14 is lighter and consequently can be made longer and wider in order to cover more plaster surface at a given time. From its resilience, the darby 10 resumes its original shape when bent and does not ordinarily acquire dents, like metal or wooden darbies. Moreover, the plaster, which ordinarily corrodes aluminum or magnesium darbies, has no corrosive effect whatever upon the present darby 10.

The modified offset double-bladed darby, generally designated 36, shown in FIGURES 3 and 4, is composed of thin solid plastic-impregnated fibrous material, such as fiberglass, without the foam core 14 of the darby 10, and of approximately uniform thickness throughout. The darby 30 has forward and rearward blade portions 32 and 34 transversely or laterally offset relatively to one another but disposed parallel to one another and interconnected by an inclined connecting portion 36. The forward and rearward edges 38 and 40 are also preferably straight and parallel to one another although offset relatively to one another by the inclined connecting portion 36. The parallel portions 32 and 34 join the inclined connecting portion 36 at junction lines 42 and 4-4 respectively. The modified darby 39 has an upper surface 46 composed of forward, intermediate and rearward upper surface portions 48, =50 and 52 respectively and a lower surface 54 composed of forward, intermediate and rearward lower surface portions 56, 58 and 60 respectively.

In the use of the modified offset double-bladed darby 30, the operator grasps the rearward blade portion 34 between his fingers and applies the forward upper surface 48 against the surface of the plaster to be smoothed. The offset relationship of the forward and rearward blade portions 42 and 34 by the inclined portion 36 enables the operators fingers to be kept clear of the plaster surface being smoothed, enables a packing or pressing effect to be exerted, and facilitates getting into corners. The modified darby 39 is especially valuable in acoustical plaster Work where the material is so heavy that it tears or pulls when ordinary darbies are used. It will also be evident from FIGURE 4 that it is inherent in the construction and use of the darby 39 for the operator to turn it upside down during use, so that the blade portion opposite the one being grasped is disposed at an acute angle to the surface being plastered and the blade edge engaged therewith rather than its fiat surface, as described above.

Both darbies of the present invention have been accepted as craft quality by plasterers, and produce a perfectly worked surface, even on acoustical plaster threequarters of an inch thick, a thickness which it would likely slide off when an ordinary darby is used.

As plaster is a thixotropic substance, it becomes more fluid when worked. With the darby herein described it is possible to finish thick sections even up to inch without excessive working, thus enabling the finishing of the plaster on vertical surfaces and overhead surfaces without its running off due to the thixtropic properties of plaster. Moreover, the darby of the present invention produces a much superior finished plaster due to the coaction of the physical properties of the epoxydmpregnated fibrous glass surface with the plaster itself. This is in marked contrast to the surface produced by conventional aluminum and magnesium darbies. These are so smooth that they draw the water to the surface of the plaster with the result that the plaster as it cures is weak and is apt to undergo crazing and other mechanical difficulties.

Because of the unusually light weight, rigidity and lack of adhesion, to the plaster, of the resin surfaces of the darbies of the present invention, they can be made longer and wider than prior metal darbies, thereby enabling the operator to cover more square footage than by the use of such prior darbies. In addition to their chemical and physical inertness to plaster, the darbies 10 and 30* also are superior to darbies presently available by possessing greater strength, dimensional stability and freedom from 3 the warping which occurs in conventional wood darbies.

The darbies 10 and 30 may also be used in brown coating, and as the straight edge tool for the putty coat or finish coat. This enables a single darby of the present invention to do the work of the two separate tools previously required, and with greater efliciency and higher quality. The construction provided by the present invention is also applicable to other tools such as the slicker, the straight edge and the rod used by the so-called trowel trades" in applying and Working hydration setting materials.

By fibrous glass material as used herein is meant fila ments of glass drawn or blown and either random deposited, pressed (felted) into mats, spool wound in continuous lengths into many parallel strands called roving or spun into yarn and Woven into cloth. The synthetic resin, such as polyester, phenolic or epoxy resin, after incorporation of the glass fibers, is polymerized into a relatively hard, inert, tough, rigid material.

What I claim is:

1. .A plasterers darby, comprising an elongated body of and with an intermediate connecting portion inclined relatively to and interconnecting said forward and rearward portions, said blade portions terminating at their junctions with said intermediate connecting portion.

2. A lasterers darby, according to claim 1, wherein said forward and rearward blade portions are disposed approximately in spaced parallel planes.

3. A lasterers darby, according to claim 1, wherein said portions are of approximately uniform thickness throughout.

4. A lasterers darby, according to claim 1, wherein said body is resilient and is composed throughout of plastic-impregnated fibrous material.

References Cited UNITED STATES PATENTS 745,679 12/1903 Schulze 15236 2,773,377 12/1956 Squire 15235.4 2,855,021 10/1958 Hoppe.

3,140,500 7/1964 Pilla 15-235.4 3,302,233 2/ 1967 Sebastiani 15--235.4

CHARLES A. WILLMUTH, Primary Examiner.

R. I. SMITH, Assistant Examiner. 

